Optical fiber connectors are an essential part of substantially all optical fiber communication systems. For instance, such connectors are used to join segments of fiber into longer lengths, to connect fiber to active devices such as radiation sources, detectors and repeaters, and to connect fiber to passive devices such as switches and attenuators. The principal function of optical fiber connectors is to hold an optical fiber such that its core is axially aligned with the optical path of the device to which the connector is mating (herein “mating device”). This way, the light from one fiber is optically coupled to the optical path of the mating device.
A typical connector comprises a housing containing a ferrule which holds one or more fibers. The ferrule is biased forward in the housing such that, when the connector is mated to the mating device, the fiber in the ferrule urges against the optical path of the mating device. There are many different prior art connectors currently available for establishing such optical connections, including, for example, SC, ST and FC connectors and more-recent “small form factor” designs such as MTRJ, MU, LC, MPX and MPO-type connectors.
In networks and communication equipment that utilize optical fibers, often optical fibers are mated in pairs corresponding to a transmitting optical fiber and a receiving optical fiber. It is essential that the connections be made correctly. For example, it is important to ensure that a transmitting optical fiber is connected to another transmitting fiber or to a transmitter port of a transceiver and that a receiving optical fiber is connected to another receiving optical fiber or to a receiver port of a transceiver.
To ensure proper polarity, duplex optical connectors have been used in the communications industry to couple two simplex optical fibers together in a duplex arrangement to allow both optical fibers to be connected simultaneously to ports located on communication equipment or to an adapter which connects pairs of optical fibers together. For example, U.S. Pat. No. 5,579,425 (hereinafter the '425 patent) discloses an optical fiber duplex connector based on the LC connector, which is shown in FIG. 3. The duplex connector is formed by joining together a pair of simplex LC connectors 51 with a plastic clip 52. Each clip 52 includes a first planar structure 53 having a pair of cylindrical pins 54 of different diameters thereon. The cylindrical pins 54 are press fit into associated openings 55 formed in the simplex connectors 1, thereby connecting them together. The plastic clip 52 has information thereon, such as the letters A and B, which identifies the correct polarization of the duplex connector with respect to its mating device (e.g., an adapter). Although the plastic clip design of the '425 patent provides a novel way for forming a duplex connector, it has been found that the cylindrical pins tend to have marginal holding strength and are generally not as robust as desired. Furthermore, since the clip is intended to augment the connector's latch mechanism—i.e., it provides the user with a larger area to actuate the latch—the connector is somewhat dependent on the clip. This dependence undermines the use of the connectors in simplex applications. In other words, by designing a connector to work in conjunction with the clip, the connector does not function as well independently, perhaps necessitating different connectors for simplex applications.
FIG. 4 illustrates another known optical fiber duplex connector. The duplex connector shown in FIG. 3 comprises two connectors 60 clipped together by a duplex yoke 61, which attaches near the back ends of the connector housings. Once the duplex yoke 61 has been attached, end portions of two strain relief boots 62 are pushed over crimp cans 63 extending from the back ends of the connector housings. Heat fit tubing 64 is attached to the fiber cable 65 and to the ends of the crimp cans 63. Each of the connectors 60 comprises a two-piece housing. The front portion 16 of the housing has a latch 67 thereon and houses the ferrule assembly (not shown) that holds the end of the optical fiber. The back portion 68 of the housing contains a metal insert (not shown) that assists the connector in handling side loading. The optical fiber cable 65 contains aramid fiber strength members that are crimped to the metal insert. As with the duplex connector of the '425 patent, the duplex yoke 61 attaches to the connector housings. The housings of the connectors 60 must be sufficiently long to enable the yoke 11 to be attached to them because the connectors 60 require the back portions 68 of the housings. As with the duplex connector of the '425 patent, the duplex connector shown in FIG. 4 is used normally on the front side of receptacles/adapters, rather than on the back side. Although this connector assembly is suitable for its intended purpose, the fact that the anti-snag guard/latch actuation pad is integral with the duplex clip militates in favor of using the connector with a duplex clip—even to a greater extent than with the connector of the '425 patent. The preference to use different connectors for simplex and duplex applications tends to increase the number of components of the connector system, thereby increasing inventory costs and, in general, adding complexity to the system.
In U.S. Pat. No. 6,409,392, a duplex clip is disclosed for coupling two simplex connectors of the type used in behind-the-wall (BTW) applications to form a duplex connector. Connectors suitable for BTW applications are typically considerably shorter in length than the two-piece connectors 50 and 60 shown in FIGS. 3 and 4, respectively. As disclosed in the '392 patent, the duplex clip comprises a clip body that is adapted to receive and grip outer surfaces of the boots of the pair of simplex connectors to hold the simplex connectors in close spatial proximity to one another, thereby forming a duplex connector. Two generally cylindrical bores are formed in the clip body and the inner surfaces of each of the bores are adapted to grip the outer surfaces of the boots. Slots are formed in the clip body to provide the bores with generally C-shaped cross-sections. Cables can be passed through the slots to enable the clip to be clipped onto a pair of simplex connectors when the simplex connectors are coupled to or decoupled from a receptacle or adapter.
Although the duplex clip configuration of the '392 patent provides for a connector which can be used in BTW applications, the applicants have identified a number of shortcomings with this configuration. First, the duplex clip of the '392 patent's requires the use of a boot on the end of the connector. Although boots are common, they are not necessary for all applications. The duplex clip of the '392 patent would be unsuitable for applications in which the boot was not used. Furthermore, the yoke configuration of the duplex clip disclosed in the '392 patent is relatively bulky and extends well beyond the periphery of the housing of the connector. This can be problematic in certain applications where there is a need to minimize the space occupied by the connector.
Therefore, there is a need for a connector system which provides for a duplex connector assembly in which the connectors used for simplex and duplex connectors are identical, and in which the clip used to form the assembly is simple and unobtrusive while nevertheless providing for a robust interconnection system that does not require the use of additional components (e.g., a boot). The present invention fulfills this need among others.